If I remember right, the D4Y was not only faster, but more nimble, which perhaps would have helped survivability and/or attack set-up?
I'd imagine the Helldiver's ability to carry a broader array of ordnance, as well as its SS tanks and armor, would make it more useful.
I do know I wouldn't want to fly any bomber in contested skies lacking SS tanks and armor, myself ... but from accounts I've read, the SB2C was a pig to fly.